1-4
888-2408-002
WARNING: Disconnect primary power prior to servicing.
Introduction/Specifications
1.3.4
PA/IPA Modules
Each PA Modules consists of two independent RF amplifiers or PAs. Each PA has
two MOSFET devices mounted on a compact heat spreading assembly and is
capable of providing up to 425 watts (850W per module). Each PA module consists
of two RF PAs mounted on opposite sides of the heatsink assembly. The RF
modules plug directly into an isolated combiner without using channel sensitive RF
cables. PA modules are “hot-pluggable” and can be removed and inserted into an
operating transmitter without removing plugs and cables. Each PA module is
conservatively rated to produce over 750 watts of output power into a system
VSWR of 1.5:1 at up to 50 degrees C ambient temperature at sea level.
The IPA consists of a standard PA Module with only one side active at a time to
provide the required drive to the 5kW PA. The transmitter contains sensing, logic
and switching circuitry which will automatically switch from a failed IPA to the
remaining one. For even further redundancy, any PA module can also be used as an
IPA module, without modification.
1.3.5
RF Combining
Each PA (one half of a PA module) is combined first in groups of eight in a
compact, “Z plane” isolated combiner. True isolation means that each module will
continue to work into a nominal 50 ohm load regardless of the number of active
amplifiers, for almost zero stress to the amplifiers during fault conditions. The
outputs of the 8 way combiners are then combined in a compact 3dB hybrid. The
3dB hybrid provides improved load conditions for the RF modules and tends to
absorb power received by the antenna. This can reduce the amount of RF
intermodulation generated by the transmitter when co-sited with other FM
transmitters.
1.3.6
Control System
A microprocessor based controller monitors over 100 operating functions of the
transmitter and makes intelligent operating decisions based on operating conditions.
Detailed system information is available using the front panel diagnostic display.
The controller is designed for direct connection to standard parallel remote control
systems.
The Controller also includes built-in logic and controls for automatically switching
to the reserve IPA section, and a backup exciter if installed. The main controller
provides automatic power control, VSWR overload protection, automatic VSWR
foldback, RF power soft start, AC restart and diagnostics. Basic control functions
available even without the main controller are VSWR protection, IPA protection,
transmitter on/off, failsafe and interlock.
The control system for the transmitter is modular and is centered on the backplane
which is also the control panel for the transmitter. Various control printed circuit
Summary of Contents for Z5 CD
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Page 192: ...6 40 888 2408 002 WARNING Disconnect primary power prior to servicing Troubleshooting...
Page 194: ...7 2 888 2408 002 WARNING Disconnect primary power prior to servicing Parts List...
